Failure due to interactions being limited to touch only on touchscreen devices

Only using touch-specific JavaScript event listeners when a touchscreen is detected

These types of approaches have historically been popular for "mobile" specific development, to ensure that touchscreen interactions are more responsive and immediate (due to the way that touch interactions used to add a delay of approximately 300ms between a "tap" interaction and the generic click event being fired).

/* inferring the presence of a touchscreen based on
   support for the Touch Events API */

if (window.TouchEvent || ('ontouchstart' in window)) {
  /* set up event listeners for touch */
  target.addEventListener('touchend', ...);
  ...
} else {
  /* set up event listeners for mouse/keyboard */
  target.addEventListener('click', ...);
  ...
}
				

/* inferring the presence of a touchscreen based on
   the CSS Media Queries 4 Interaction Media Features
   match for a "coarse" primary input mechanism */

if (window.matchMedia && window.matchMedia("(pointer:coarse)").matches) {
  /* set up event listeners for touch */
  target.addEventListener('touchend', ...);
  ...
} else {
  /* set up event listeners for mouse/keyboard */
  target.addEventListener('click', ...);
  ...
}
				

Similarly, web content that omits relevant/necessary keyboard event listeners (e.g. for the correct keyboard interaction with a complex widget, such as a tab interface) when a touchscreen is detected - under the assumption that on a touch device, keyboard support won't be necessary.

/* inferring the presence of a touchscreen based on
   the navigator.maxTouchPoints property defined in
   the Pointer Events API */

if (!(window.PointerEvent && ('maxTouchPoints' in navigator) &&
    (navigator.maxTouchPoints > 0))) {
  /* set up event listeners for keyboard interactions */
  target.addEventListener('keyup', ...);
  ...
} else {
  /* no need to listen to keyboard - there's a touchscreen... */
  ...
}
				

Generally, these approaches will also result in a failure of Success Criterion 2.1.1 Keyboard - but only in situations where a touchscreen interface was also detected.

Hiding/omitting controls for mouse users when a touchscreen is detected

Web content containing interactive widgets such as content carousels, with visible buttons to operate the widget (such as previous/next buttons, or a visible scrollbar/slider). These visible controls are hidden/omitted when a touchscreen is detected, under the assumption that users will simply use touch gestures to operate the widgets.

/* using CSS Media Queries 4 Interaction Media Features
   to hide particular elements in the page (such as a container
   with visible controls) when a "coarse" primary input is present */

@media (pointer: coarse) {
  #widget .controls { display: none; }
}
				

Generally, these approaches will also result in a failure of Success Criterion 2.1.1 Keyboard and (depending on the touch gesture that the user is expected to perform) Success Criterion 2.5.1 Pointer Gestures.